干旱区生态环境知识资源中心

Perennial grasses have received particular attention as bioenergy crops in recent years due to their high biomass productivity and environmental benefits. The objective of the present study was to compare four perennial grasses: miscanthus (Miscanthus x giganteus Keng), switchgrass (Panic= virgatum L.), giant reed (Arundo donax L.), and bulbous canary grass (Phalaris aquatica L.) in terms of biomass yield, energy balance, and biomass quality under four nitrogen fertilization rates (0, 100, 150, 200 kg ha(-1)y(-1)) and 2 harvest times (autumn, winter) over three growing seasons in the Mediterranean environment of Turkey. The crop biomass and net energy yields were optimized with none or 100 kg ha(-1) y(-1) N input in the study. Although the winter harvest resulted in significant yield reductions in all of the grass species, it improved the biomass quality of miscanthus, switchgrass, and giant reed due to reduced moisture and ash contents. On the contrary, the autumn harvest resulted in a considerably lower moisture and ash contents in bulbous canary grass, mainly because of leaf defoliation the during summer dormancy period. Giant reed produced the highest average biomass yield (between 12.86 and 36.78 t ha(-1)) over the three years, followed by miscanthus (between 12.75 and 23.54 t ha(-1)), switchgrass (between 11.88 and 18.91 t ha(-1)), and bulbous canary grass (between 5.21 and 10.83 t ha(-1)). On the other hand, bulbous canary grass provided the highest average energy ratio (19.7-64.5) over the three years, due mainly to a lack of energy input for irrigation. These results suggest that satisfactory biomass production can be achievable from miscanthus, switchgrass, and giant reed in the semi -arid Mediterranean environment under adequate moist conditions, but the irrigation requirement increases the energy cost, thus decreasing the energy ratio. In this respect, bulbous canary grass may be evaluated as an alternative bioenergy crop in the dry marginal lands of Mediterranean for sustainable biomass production.